(1) Field of the Invention
The present invention relates to a technical field of video output technology.
(2) Description of the Related Art
The video output technology is a technology for playing back video information that has been recorded on a recording medium or transferred over a transmission path, and outputting a video signal by a method that corresponds to a mode in which the playback apparatus is set.
In conventional technologies, typically a video signal of 60 frames/sec is used so that the television receivers can play back the received video signal. In recent years, however, monitors and projectors supporting the frame frequency of 24 frames/sec have been put into markets.
Such products have started to be put into markets because the video signal of 24 frames/sec is expected to be used more increasingly for the main movie provided in BD-ROM for sale, the BD-ROM being a next-generation optical disc. This is because images of a higher quality can be obtained when the video signal of 24 frames/sec is used for the main movie since the video signal is generated from a source that is a film on which the vide image is recorded at 24 frames/sec. Further, this will meet the demand of the market for higher-quality images.
The prior art concerning the video output technology includes Patent Document 1 (Japanese Patent Application Publication No. 2001-223983 (FIG. 1)) and Non-Patent Document 1 (“AV Review”, No. 87, Ongen Publishing Co., Ltd., 1999).
Meanwhile, a connection method conforming to the HDMI (High Definition Multimedia Interface) standard is often used in the connection between a BD-ROM player and a monitor. In the HDMI connection, the connected apparatuses synchronize with each other when transferring data therebetween. As a result, when the frame frequency is switched from one to another, the apparatuses need to re-synchronize with each other. The re-synchronization process may take several seconds, and the video output is stopped during the re-synchronization. Also, when a connection method other than the HDMI connection is used, namely, a connection method that does not require the re-synchronization process is used, the display on the monitor may be disordered or interrupted if the frame frequency of the video signal changes rapidly.
Here, generally, in package software provided in the BD-ROM, the main movie is recorded as a video signal of 24 frames/sec, and most of the sources of video images other than the main movie, such as a menu or a bonus movie like the making of the main movie, are not recorded on films, and are recorded as video signals of 60 frames/sec. For this reason, if a playback path from the menu to the main movie, which differ from each other in the frame frequency, is selected during a playback of the package software, the video output may be stopped for several seconds due to the re-synchronization process according to the HDMI standard.
Even if a high-quality image is achieved by providing the video output at 24 frames/sec, a sudden stop of video output for several seconds will be felt by the user as a problem that may cause the user to complain about the product.